Flow cytometry has become the essential tool for cell-based assays. Yet these versatile machines are technologically complex and the equipment expensive requiring shared use and the development of core facilities. Currently, the Department of Medicine (25 different NIH-funded users) accounts for the majority of the campus-wide use of flow cytometry. The increased demand from the Department of Medicine and elsewhere at CUMC has justified the development of an internally funded Imaging and Cytometry Core, headed by Dr. Clynes. This is part of a larger institutional effort to build translational research in medicine, including the newly created Center of Translational Immunology. This proposal, in particular, joins 8 multidisciplinary biomedical researchers (whose NIH funded research totals >$15,000,000/year), and seeks to integrate immunologists with specific expertise in flow cytometric techniques with investigators studying inflammation in cancer, the lung, and the atheromatous plaque. This will create a shared resource for use, training, maintenance and of the versatile LSR II flow cytometer throughout the School of Medicine at CUMC. Examples of NIH funded research that this Core will support include: stem cells/myeloid suppressor cells in cancer, transplantation rejection and tolerance, resolution of atherosclerosis and therapeutic blockade of immunoglobulin receptors in type I diabetes. The requested LSR II requires three optional and costly accessories to permit and expedite these translational studies. 1. The UV laser permits immunoreceptor signaling (calcium flux), side population detection, and cell cycle analysis. 2. The yellow-green laser broadens the cytometers capacity to detect a wide variety of red flourochromes, including Red Flourescence Protein, important for cell lineage analysis, gene expression and protein trafficking, dramatically increasing versatility. 3. The 96-well attachment will allow high throughput analysis of CFSE proliferation assays, multiple analytes, expediting assessment of inflammatory cytokines in large sample format of tissue cells/blood and cultured primary cells eliminating the need for time-consuming ELISA based assays. In sum the LSRII will catalyze the development of a versatile and user-friendly Cytometry Core for over 25 NIH-funded investigators in the Department of Medicine and will make manifest the integration of the Center of Translational Immunology within the general community of the School of Medicine.